Three KCSE candidates have been found with two guns, bhang and other stolen items.
They are currently sitting their examinations at Kilimani Police Station after they were arrested on Tuesday.
Nairobi County Commander Japheth Koome confirmed the arrest, saying the three had attacked a pedestrian on November 4 in Jamhuri area, Nairobi, and robbed him of his shoes, laptop, mobile phone, assorted clothes and a bottle of perfume.
"The victim managed to identify one of the attackers and reported the matter to police," Koome said.
Two are students of Soweto Baptist High School while one is a candidate at Kangemi High School.
Koome said the three suspects will be arraigned in court on Friday.